The field of the invention is lens mounts for optics having axial adjustment. The present invention is particularly concerned with an apparatus for focusing an optics and consists essentially of a guide cylinder and of a tube guided therein or thereon and containing at least a portion of the optics, and in this device the cylinder and the tube are mutually displaced by means of a rotational motion converted into a linear motion for the purpose of focusing the optics.
Such a prior art lens mount is disclosed in U.S. Pat. No. 3,677,155, the disclosure of which is incorporated therein.
U.S. Pat. No. 3,677,155 discloses, among other things, a lens mount for a photographic objective having an optical axis, a stationary tubular mount adapted to be attached to a camera body, a range adjustment ring rotatably supported on the mount member, a lens barrel arranged coaxially inside the stationary mount member and means for mechanically interconnecting the range adjustment ring and the lens barrel* in the direction of the optical axis upon rotation of the range adjustment ring. FNT *for displacing said lens barrel
According to the prior art the optics are mounted in a system which is referred to as a "helical lens mount" wherein the guide cylinder and a coaxial tube are operationally connected by Acme or V threads having several turns and have corresponding pitches and are moved with respect to each other by hand or by a motor.
Such a prior art apparatus suffers from the drawback that its high sliding friction between the guide cylinder and the tube requires energy output to overcome the friction by hand or by motor. In particular where focusing is by means of a motor, this focusing requires bigger motors and high capacity energy sources. In photographic cameras for instance, there results the need for relatively large, cumbersome energy source containers.